The Organic Center Seeks Organic Solutions for Citrus Greening

Citrus greening disease, also known by its Chinese name Huanglongbing, threatens the citrus industry on a massive scale. It has devastated millions of acres of citrus crops throughout the United States and abroad, ravaging citrus in countries in Asia, Africa, and South America. The highly destructive disease can spread quickly, and once a tree is infected it cannot be cured.

Citrus greening is spread by the Asian citrus psyllid, a small insect that transmits the disease as it feeds on the leaves and stems of citrus trees. These psyllids are prolific breeders, with each female laying up to 800 eggs. Some trees can be infested with 40,000 psyllids at any one time. Infected trees produce green, misshapen bitter fruits that are unsuitable for sale, and most infected trees die within a few years.

Since 2006, citrus greening has cost over 4.5 billion dollars in lost revenue in Florida alone and has been responsible for the loss of over 8,000 jobs. Citrus greening and Asian citrus psyllid threatens to continue to devastate the Florida industry and fear of it arriving is beginning to affect the California, Arizona, and Texas citrus industries as well.

Unfortunately, most of the research efforts toward controlling citrus greening focus on methods such as chemical controls and genetic modification of citrus trees that are not compliant with organic standards.

These conventional strategies have not yet proven effective and have contributed to policy decisions that are not compatible with organic management. For example, applications of synthetic pesticides have been mandated as an eradication method in California citrus groves, including certified organic groves, in regions where the psyllid has been detected, but no organic alternatives have been offered as substitutes for these mandatory spray regimes.

To save organic citrus, additional research on organic-compliant methods for controlling citrus greening is needed. The Organic Center is raising funds to fully support a three-year research project in collaboration with Ben McLean of Uncle Matt’s Organic and University of Florida researchers Michael Rogers, Ron Brlansky, Phil Stansly, Jawwad Qureshi, and Fritz Roka. The Organic Center is taking a multidisciplinary approach to the work in order to develop a holistic approach to controlling the disease. They are targeting four strategies:

Examining the efficacy of organic materials. To determine the efficacy of labeled organic pesticides for controlling the Asian citrus psyllid, Dr. Michael Rogers will conduct field tests of labeled organic insecticides including pyrethrins and Neem oil extracts, biological materials such as Chromobacterium (the active ingredient in Grandevo) and Beauveria (the fungal spore that is the active ingredient in Mycotrol), and enhancement of these materials via use of filtered molasses and organic oil-based surfactants as adjuvants.

Evaluating trees that are showing resistance to citrus greening and investigate the potential to breed naturally resistant varieties. Dr. Ron Brlansky is cooperating on this project, which will evaluate rootstock and scion material from trees that are showing very high levels of resistance.

Examining how the organic materials interact with natural insect enemies to the psyllid and pollinators. Drs. Phil Stansly and Jawwad Qureshi will work with a variety of organic citrus growers to analyze the best practices for applying organic materials to ensure that they do not harm parasitoids and other predatory insects.

The Organic Center also plans to develop a manual that translates research findings into a state-by-state guide for organic control of psyllids.

This multifaceted approach will be critical for providing growers around the country—organic and conventional—with the information they need to protect their citrus groves from collapse due to citrus greening. It will also be useful in providing policymakers with organic alternatives to Asian citrus psyllid control to incorporate into area-wide treatment protocols.

If it is not stopped, citrus greening may remove citrus from our diets, destroy countless farms, and completely disrupt regional economies. Without further research on organic methods for controlling the disease, the entire domestic organic citrus sector may disappear.